A variety of dog clutch mechanisms have been described by others—U.S. Pat. No. 4,977,989; US2,010/0276245 U.S. Pat. Nos. 7,055,664B2; 3,834,500; 7,413,067B2; 4,529,080. In some applications typically involving high speeds and/or torques it is desirable that a degree of precision be achieved in the engagement and disengagement of the clutch such that engagement times are minimised by reducing the disengaged axial clearance to a minimum. It is also desirable that unwanted forces be avoided such as the bending forces that would be imposed on the fork by over stroking on engagement and also the wear and friction that would be imposed on the fork if it was under continuous load whilst engaged or disengaged. Thus it is desirable that the axial stroke length be also accurately controlled. Thus it is desirable that both the position of the fork in relation to the clutch faces and the stroke length of the fork be accurately controlled. To achieve the required precision without an adjustment mechanism would require excessively close manufacturing tolerances of the individual components to avoid excessive build-up of tolerances in the final assembly. Such close tolerances in manufacture result in an undesirable increase in costs.
An adjustable clutch mechanism which attempts to meet these requirements has been described by Erlebach U.S. Pat. No. 5,573,096. In that arrangement the required stroke length in the axial direction is determined by a stop ring whose length in the axial direction determines the stroke length. Different length stop rings may be selected. The requirement to have different length stop rings to accommodate various tolerance build-ups to give the precise required stroke length is an inconvenient aspect of the above mentioned system.
Adjustment of known clutch mechanisms typically requires at least partial disassembly of the differential or other assembly in which the clutch mechanism is incorporated. This is both inconvenient and time consuming.
The present invention is directed towards providing an improved shifting device which overcomes the aforementioned problems.